SPS-b-PMMA

Figure 19.10 DSC curve comparison between (a) an SPS-t-OH polymer and (b) the corresponding SPS-b-PMMA.

TABLE 19.4 Summary of SPS-b-PMMA and SPS-b-PBMA Diblock Copolymers... 

NMR spectra of a starting styrene/B-styrene copolymer containing 1 mol % B-styrene units (after hydroxylation) and two corresponding SPS-g-PMMA graft copolymers with 20 and 59 mol % MMA contents, respectively. In addition to the major peaks at 1.32,1.85,6.65, and 7.15ppm for the protons in the SPS backbone, the distinctive peak at 3.58ppm corresponds to methoxyl groups (CH3-O) in the PMMA. 

Figure 19.7 NMR spectra of (a) SPS-OH containing 1 mol % OH units and two corresponding SPS-g-PMMA graft copolymers with (b) 20 and (c) 59 mol % MMA contents, respectively.

Figure 7 illustrates the GPC curves of poly(TrMA) obtained by LiAn in toluene (A) and THF (B) Figure 8 is the GPC curves of the PMMA derived from the poly(TrMA) obtained with Sp-BuLi. Both polymers obtained in THF with LiAn and Sp-BuLi showed rather narrow distributions and initiator efficiency was about 100%. The polymerization in toluene was complicated and a large portion of the initiators was consumed for the formation of oligomers. 

Photoisomerization of both DE and SP clearly occurs in films of PMMA. Spectra (not shown) taken before and after several amounts of UV and green irradiation exhibit shape changes and isosbestic points at about 329, 377, and 429 nm for DE and 317, 339, and (less pronounced) 440 nm for SP. These spectra clearly demonstrate the forth A- B and back B— A photoiso-... 

As was the case for SP and o dyes, the fitted slopes, p(A) and p(AA), of the early time evolution of Ag and AAg, respectively, showed a linear dependence on the irradiation light intensity for both UV- and green-light-induced orientation, and the solid tines in Figure 3.21(A) are linear theoretical fits by Equations 3.14 and 3.15. The value of Sg of DE in PMMA, obtained at the photostationary state of UV irradiation for different irradiation intensities and wavelengths, is fairly constant, i.e., -0.060 and -0.024 for 365 and 405 nm irradiation, respectively, a feature that is theoretically rationalized by Equation 3.27. Indeed, Equation 3.20 dictates that for a system without B—>A themal isomerization, 2(cos w) i.s given ai the photostationnary state by ... 

Positive-ion DE-MALDI-TOF mass sp>ectra of a PEG / PMMA blend recorded adopting different delay times grid voltage % values, (a) 4600 ns and 88% (b) 100 ns and 96% and (c) 2800 ns and 96%. (Reprinted with permission from Ref. 88, Copyright 1999 John Wiley Sons Ltd)... 

Most of the SPS-t-B polymer was suspended in benzene and was subjected to the oxidation reaction by oxygen in the presence of free radical polymerizable monomers, that is, MMA and n-butyl methacrylate (BMA). As illustrated in Scheme 19.2, the SPS-t-B was selectively oxidized and transformed to a stable polymeric radical for the polymerization of MMA and BMA. The resulting reaction mixture was carefully fractionated by Soxhlet extraction using boiling THF to remove any PMMA or poly(butyl methacrylate) (PBMA) homopolymers. In most cases, only a very small amount (about 10%) of homopolymer was present, which may have been initiated by the radical in a bicyclic ring... 

Run T (°C) SPS-t- B(g) O2 (ml) Polar Monomer Reaction Time (h) Yield (g) Polystyrene Block PMMA Block ... 

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